Bitkeeper is a source management system comes under the category of distributed version control. It is an open source software get the license under Apache 2.0. Version control is a collection of repositories and as Bitkeeper is a distributed software configuration management, you can store the archived copy locally. The source is just a command line interface so it is very easy to understand and use.
Bitkeeper is compatible with the OS platforms such as Linux, Windows, Os x, BSD, and Solaris. So, you can download and install the appropriate version applicable to your OS or you can download the source directly.